NITEROI, BRAZIL - AUGUST 5: Fresh prawns are displayed at the Mercado São Pedro, the St. Peter's fresh fish market, on August 5, 2009 in Niteroi in Brazil. Stating in its website that fish is a good source of protein, not high in saturated fat, and a good source of omega-3 fatty acids, the American Heart Association recommends eating seafood at least twice a week. (Photo : Photo by David Silverman/Getty Images)

Doctors recommended a diet rich in "good" cholesterol (HDL) and minimal "bad" cholesterol (LDL) as the way to an optimal healthy heart. However, a recent study revealed that lowering one's intake of food rich in saturated fats which raises LDL level in the blood, did not result to a healthier heart even though it did lower blood cholesterol. In fact, it had the opposite effect - lower cholesterol level corresponds to an increased risk of dying.

The new study utilized data from a clinical trial called Minnesota Coronary Survey which runs for 4.5 years from 1968 until 1973. Data from more than 9,000 institutionalized men and women in six Minnesota state mental hospitals and one nursing homes. A control group, comprised of about half of the participants, were given a diet with 18 percent saturated fat, 5 percent polyunsaturated fat, 16 percent monounsaturated fat which also had 446 mg dietary cholesterol per day.

On the other hand, the rest of the subjects received a "healthier"diet with its lower saturated fat percentage and lower dietary cholesterol content. This healthy diet consists of 9 percent saturated fat, 15 percent polyunsaturated fat, 14 percent monounsaturated fat with a 166 mg dietary cholesterol. The increase in unsaturated fat was done by introducing linolenic acid which is an omega-6 polyunsaturated fat in corn and soybean oils and margarine.

In the study, researchers only included 2.403 participants who were on either diet for around a year. By the end of the one-year period, the group who were on the unsaturated fat diet had lower blood cholesterol which was expected. What was unexpected was that participants who had lower cholesterol levels during the study actually had a higher risk of dying. What is even more perplexing is that this trend is consistent in both the saturated fat and unsaturated fat participants reports CNN.

Researchers found in this study, a 30 mg/dL decrease in blood cholesterol level corresponds to an alarming 22 percent increased risks of mortality. This runs counter to the current position taken by the medical establishment that a lower cholesterol level means a decreased risk of heart disease and stroke. In fact, doctors would often advise patients to take cholesterol-lowering drugs to decrease cholesterol levels to what is perceived to be the normal range.

However, not all are convinced of this belief that cholesterol should be lowered to prevent heart disease. For instance, Dr. Bradford Weeks, MD, calls this view too simplistic and cites evidence that low cholesterol is actually dangerous. This view is also shared by Dr Mercola, who states that low cholesterol could cause memory loss, dementia, depression, cancer and even accentuate suicidal tendencies.

For now, it is still too early to change existing dietary guidelines based on this single study. Obviously, more research is needed to confirm the observed link between low cholesterol and increased mortality rate and to determine what level is indeed safe. But the study does make one think of the merit of the current medical practice of almost indiscriminate prescription of cholesterol-lowering drugs, highlighted by the video below.